Frogs, Bats, and Bees: Why Are Fungal Infections Wiping them Out?

We’ve written before about fungal infections devastating amphibian, honey bee, and bat populations, but this winter we wanted to delve more deeply into this issue. First, we’ll learn a bit about fungi and why they can be such virulent pathogens. In the next few posts, we’ll explore the emergence of these infections in bats, honey bees, frogs, and yes, even in humans.

Killer airborne fungus. Photo from National Geographic, courtesy of Edmond Byrnes and Joseph Heitman, Duke Dept. of Molecular Genetics and Microbiology

What is a fungus?

A fungus is not an animal or a plant. It isn’t a bacteria either. Fungi belong to a separate kingdom that includes molds, yeasts, lichens, and mushrooms. Animals and fungi do share certain features: they breathe oxygen and get energy by eating food. Their cells are similar. Yet fungi don’t eat and digest their food as animals do. Their feeding style breaks down dead plants and animals, decomposing them. But they can also switch their diet from dead animals to live cells.

Fungi can retreat into spores and survive for long periods without food. They can live independently, outside their hosts. As spores they can float through the air, get lodged into the treads of a shoe, or float in water. Unlike bacteria and viruses that may burn themselves out when they kill their victims, fungi can wipe out whole populations without being destroyed themselves.

Why are certain types of animals so vulnerable to fungal diseases?
There isn’t one conclusive answer. Those animals that are immunosuppressed, however, tend to be more vulnerable to fungal infection. But why are these animals so unhealthy? The answers are complex and may have to do with many different causes, perhaps a “perfect storm” of causes: the overall decrease of biodiversity, use of pesticides, climate change, clear cutting of forests and habitat destruction and degradation, and other issues.

Readers of Frogs Are Green are familiar with the the chytrid fungus, Batrachochytrium dendrobatidis, which has wiped out hundreds of species of amphibians.

In 2006 the white-nose syndrome, an infection caused by the fungus Geomyces destructans killed a few bats in New York; since then it has killed more than 5 million bats in 21 states and four Canadian provinces.

Recently honey bee populations have been devastated. There is evidence that co-infection with multiple pathogens, including fungi, is one cause.

A fungus called Cryptococcus neoformans ravages humans with compromised immune systems. It is spread primarily by the guano of pigeons and contracted by inhaling spores. More than 1 million immunosuppressed patients are infected annually around the world.

What is the Causing the Spread of the Emerging Fungal Diseases?

Fungal spores can be easily spread by humans so fungi that were once isolated in different parts of the world can now exchange genes and create new and more virulent pathogens.

As reported in a recent e360 (Yale) article: “Fungi have driven more animal species extinct than any other class of pathogens by quite a long way,” according to Matthew Fisher, an epidemiologist at Imperial College in London.

As Rob Miles, executive director of the Organization for Bat Conservation told Bee, Bat, Frog Deaths May Be Linked, Discovery News”>Discovery News, “It appears that many species are under an immense amount of stress, allowing opportunistic diseases to take hold.”

Information from this post from:

A Rise in Fungal Diseases is Taking Growing Toll on Wildlife by Michelle Nijhuis, Slate

Bee, Bat, Frog Deaths May Be Linked, Discovery News


Today is Save the Frogs Day!

Today is Save the Frogs Day, organized and created by conservation biologist Dr. Kerry Kriger. Tune in to hear an interview today with Dr. Kriger at 4:30 US Eastern or 1:30 PST (Sirius 112/XM 157) on Martha Stewart Living Radio.

As it’s been almost a year since we began the Frogs Are Green blog, we thought we’d share some thoughts about it with you. At first when we told our friends and family we were starting a blog to increase awareness about the global amphibian decline, they were a bit mystified, even amused. But I’m happy to say that a year later, almost all have become enthusiastic supporters. So we’d like to give you a few “talking points” in case you come across people who say with skepticism—frogs needs saving? Huh?

Frogs, of course, are not the only animals that need help, and we are personally involved with efforts to save other animals, particularly marine animals. But amphibians as a class of animals are threatened with extinction. That’s like saying that all mammals might soon be extinct. This is the largest mass extinction since the dinosaurs. Frogs have survived for 360 million years (and were on Earth long before the dinosaurs) and yet one-third or more of frog species are in danger of extinction.

Frogs are bioindicators—they reflect back to us the environmental health of our planet. Their permeable skin makes them especially vulnerable to environmental contaminants, such as agricultural, industrial, and pharmaceutical chemicals, particularly endocrine disruptors.  Frogs are manifesting reproductive deformities and hormonal disorders, possibly as a result of the stew of chemicals in the water in which they live. As endocrine distruptors are in the water we drink and are in dozens of consumer products we use everyday, we have reason to be concerned. Some scientists believe that an increase in the incidence of newborn baby boys born with genital deformities might be due to endocrine disruptors they have absorbed in utero.

Biodiversity is of critical importance to all of us—scientists still don’t fully understand how all elements interact in an ecosystem, but we do know that disasters occur when we alter even one small part of it (by introducing nonnative species etc). Frogs form an important part of ecosystems as both predator and prey.

While there is no cure yet for the chytrid fungus devastating frog populations, it should make us pause to consider that a whole class of animals could be wiped out by a worldwide fungus. Why aren’t frogs able to fight this off this infection? What are the underlying causes of the fungus? There are so many questions that need answers.

Frogs are subject to all the usual environmental woes—habitat loss, pollution, global warming, overcollection, invasive species. By helping frogs, we help other animals that might not have such a high profile (although frogs have a pretty low profile, all things considered). By focusing on the rainforest frogs, for example, we also help preserve the rainforest and its animals.

Frogs are part of our cultural heritage—our folktales, fairy tales, myths, children’s stories, and legends. In many cultures, they are a symbol of good luck, fertility, healing, prosperity, and are associated with rain and good harvests. And don’t forget our friends Kermit, and Frog and Toad, and Mr. Toad.

The amphibian decline is an environmental issue that you can do something about, possibly in your own backyard or neighborhood. We recently received a comment from a man in Georgia who decided not to fill in a pond on his property because he noticed that several frog species live in the pond. Another commenter from Pennsylvania has asked how he can create a frog pond in his backyard. You can lend your voice to land conservation efforts that protect vernal pools, for example.

Rachel Carson warned in her 1961 book Silent Spring about a world without birds. Can you imagine a world without frogs? Frogs, after all, are the Earth’s most ancient singers. We want to continue to hear their choruses for a long, long time.

So as you enjoy Save the Frogs day, listen to some frog songs. And please join us in helping to save frogs. We’d love to hear from you.